How do you make a sundae?

It really just refers to the glass it’s served in; otherwise it’s just ice cream. Like how highball or collins glasses often make the drink.

The vessel is called a sundae glass or tulip glass. It usually has a base, a stalk, and a cup with flared edges. Any ice cream in that glass is a sundae, though usually it has fixings like syrups, sprinkles, chopped nuts, fruit.